Under 35 U.S.C. xc2xa7 119 this application claims the benefit of co-pending Japanese Patent Application No. 2001-247199, which was filed Aug. 16, 2001, and is incorporated herein by reference.
In many applications, such as optical measurement, optical communications, and optical storage, it often is desirable to measure the transient behaviors of optical signals. As improvements in optical technologies push optical data rates higher, however, there is a corresponding need for optical measurement systems that can accurately measure the resulting high speed optical data signals. Conventionally, the transient pulses of high speed optical signals may be measured by a variety of different optical measurement systems, including sampling optical oscilloscopes.
Referring to FIG. 1, in one exemplary implementation, a sampling optical oscilloscope 10 includes a lens 12 for focusing an input light signal, which may be received from, for example, an optical fiber 14. Sampling optical oscilloscope 10 also includes a sampling streak tube 16, which includes a photocathode 18, an acceleration electrode 20, a sweep electrode system 22, a slit plate 24, and a phosphor screen 26. Photocathode 18 converts incident light received from lens 12 into electrons, which are accelerated toward sweep electrode system 22 by acceleration electrode 20. Sweep electrode system 22 performs a high speed sweep (i.e., deflection of electrons along a particular direction) across slit plate 24, transforming time variations of the incident light intensity into spatial electron density variations at different positions on slit plate 24. Slit plate 24 includes a slit 28 that allows a sample of the swept electrons to reach phosphor screen 26, where the sampled electrons are converted into light that is detected by a photomultiplier tube 30.
Referring to FIG. 2, U.S. Pat. No. 5,719,623 discloses a multi-channel streak camera 32 that includes an optical lens 34 that converts a subject 36 into a subject image 38. A converter 40 converts the subject image 38 into a plurality of divided micro-incident electronic images 42, 44, 46 consisting of pixels that are separated by a predetermined spacing. The photoelectrons corresponding to the micro-incident electronic images 42-46 are passed through openings 48, 50, 52 of a focusing electron lens 54, which focuses each of the micro-incident electronic images 42-46. A sweep electrode system 56 sweeps each of the focused electron beams in a particular direction. The swept electron beams then are focused on an output plane 58. In this way, variations at different locations in the subject image 38 during the same periods of time may be detected as spatial variations in parallel. In addition, because the subject image is divided into a plurality of smaller micro-incident electronic images, the focusing electron lens 54 may be relatively short in length, reducing space-charge effect blurring.
In one aspect of the invention, an optical pulse measurement system includes an optical signal divider and an optical signal conversion system. The optical signal divider has an optical input for receiving an input optical signal, multiple optical outputs, and a set of multiple optical channels. The optical channels are coupled between the optical input and respective optical outputs and are operable to delay propagation of optical signals, which are divided from the input optical signal, from the optical input to respective optical outputs by different respective amounts of time. The optical signal conversion system is coupled to the optical signal divider optical outputs and is operable to convert temporal intensity distributions of light that are received from the optical signal divider optical outputs into respective spatial intensity distributions in parallel.
In another aspect, the invention features an optical pulse measurement method. In accordance with this inventive method, optical signals are divided from an input optical signal. Propagation of the divided optical signals is delayed by a first set of different respective amounts of time. Temporal intensity distributions of the delayed optical signals are converted into respective spatial intensity distributions in parallel.
Among the advantages of the invention are the following.
Because the invention converts temporal intensity distributions of light that are received from multiple optical channels into respective spatial intensity distributions in parallel, the invention enables the time waveform of an input optical signal to be measured quickly. In addition, because the divided light signals that are transmitted through the multiple optical channels are delayed by different respective amounts of time, the invention enables the time waveform of high speed input optical signals to be measured with excellent temporal resolution.
Other features and advantages of the invention will become apparent from the following description, including the drawings and the claims.